It has been known for many years that asphaltic binders can be made by admixing 5 to 10 wt. % of sulfur with asphalt and subjecting the mixture to a heating step where the temperature of the mixture is kept at 500.degree. F. for a considerable period of time. Such asphalt binders were reported to be more flexible in cold weather than an untreated asphalt, and such products were reported to be valuable in binding vegetable fibers, see for instance, U.S. Pat. No. 1,264,932.
In the specific application of asphalt compositions in modern road construction, asphalts must have certain properties as these compositions are to be used for public roads. Particularly in areas with severe winters, asphalts are required to have a very high ductility at low temperatures. Thus, for example, there is a requirement for the ductility of asphalt to be at least 8 cm for a 60/70 penetration asphalt at 39.2.degree. F. in one area of the United States. A low ductility of an asphalt composition describes the possibility for the asphalt to become brittle at low temperatures. This property of asphalt is undesirable, particularly when the asphalt is used in road constructions that are exposed to heavy loads, also during the winter months.